the physiological characters of true species. Unions between these
stocks, and still more between the half-breeds arising from their
mixture, are affirmed to be either infertile, or less fertile than
those which take place between males and females of either stock under
the same circumstances. Some go so far as to assert that no mixed
breeds of mankind can maintain themselves without the assistance of
one or other of the parent stocks, and that, consequently, they must
inevitably be obliterated in the long run.

Here, again, it is exceedingly difficult to obtain trustworthy
evidence, and to free the effects of the pure physiological experiment
from adventitious influences. The only trial which, by a strange
chance, was kept clear of all such influences--the only instance in
which two distinct stocks of mankind were crossed, and their progeny
intermarried without any admixture from without--is the famous case
of the Pitcairn Islanders, who were the progeny of Bligh's English
sailors by Tahitian women. The results of this experiment, as
everybody knows, are dead against those who maintain the doctrine of
human hybridity, seeing that the Pitcairn Islanders, even though they
necessarily contracted consanguineous marriages, throve and multiplied
exceedingly.

But those who are disposed to believe in this doctrine should study
the evidence brought forward in its support by M. Broca, its latest
and ablest advocate, and compare this evidence with that which the
botanists, as represented by a Gaertner, or by a Darwin, think it
indispensable to obtain before they will admit the infertility of
crosses between two allied kinds of plants. They will then, I think,
be satisfied that the doctrine in question rests upon a very unsafe
foundation; that the facts adduced in its support are capable of many